This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 092117862 filed in Taiwan on Jun. 30, 2003, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The invention relates to a display panel, an electrode substrate and an electrode panel thereof and, in particular, to a display panel of a flat panel display, an electrode substrate of a flat panel display, and an electrode panel of a flat panel display.
2. Related Art
Referring to FIG. 1, the currently used electrode substrate 4 of a flat panel display includes a substrate 41, an electrode layer 42, and a conductive layer 43. The electrode layer 42 is disposed on the substrate 41, and the conductive layer 43 is disposed on the electrode layer 42. The material of the conductive layer 43 is selected from low resistance metals or the alloys thereof, such as a commonly used chromium or silver alloy.
In the manufacturing processes of the flat panel display, an etchant is used to etch the conductive layer 43 of the electrode substrate 4 into required pattern of conductive lines or the pattern of auxiliary conductive lines. Then, a light-emitting region and a corresponding electrode are formed above the electrode substrate 4, and finally the electrode substrate 4 is combined with a driving device (e.g., a driving chip) to form the display panel.
During the process of forming the pattern of conductive lines or the pattern of auxiliary conductive lines on the electrode substrate 4, a photoresist layer 5 is provided on the conductive layer 43 (e.g. silver alloy), and a patterned mask 6 is then set on the photoresist layer 5. At the meanwhile, an ultra-violet light (UV light) is illuminated, as shown in FIG. 2. Thereafter, a development step is performed. Finally, the etchant is used to etch the conductive layer 43 into required pattern of the conductive lines 431. However, the conductive layer 43 (e.g. silver alloy) tends to be oxidized (becomes black) owing to the exposure of the UV light, thereby increasing the resistance of the conductive layer 43 and reducing the adhesion force between the conductive layer 43 and the photoresist layer 5. Meanwhile, in the subsequent processes, the driving device (e.g. driving chip) is pressed and adhered onto the conductive lines 431, the oxidized conductive lines 431 cannot be easily adhered to the driving device. The driving device tends to be peeled or separated from the conductive lines 431, thereby influencing the reliability of the display panel. In addition, when the display panel works, the conductive lines 431 also tend to react with the external oxygen or sulfur. Thus, the conductive lines 431 tend to be oxidized or even burnt out owing to the heat generated when the current flows therethrough.
In viewing the above, a commonly used active matrix liquid crystal display (AM-LCD) utilizes the metal conductive lines, which are made of transition metals such as manganese (Mn), chromium (Cr), tantalum (Ta), or the alloys thereof When forming the metal conductive lines by thin-film deposition, the thickness of the metal conductive lines should be contracted so as to obtain good step-coverage. However, the thinner metal conductive lines may increase the resistance of the conductive lines, resulting in that the RC-delay of signals is enlarged. Therefore, the size of the flat panel display composing of the transition metals is restricted. To manufacture large size flat panel display, the manufacturing process or material for forming the metal conductive lines with ultra-low resistance is necessarily developed.
In the view of metal conductive line manufacturing process, the thicker and wider metal thin film is employed to obtain lower resistance. The thicker metal thin film, however, has the drawbacks of worse adhesion and pinhole formation. In the current moment, although a special taper etching process is used to improve the drawbacks, the manufacturing cost is increased accordingly. Moreover, the wider metal thin film not only decreases the aspect ratio of the pixels, but also increases the parasitic capacitance of the conductive lines. Thus, the thicker and wider metal conductive lines can not be applied to flat panel display.
Recently, those skilled in the art have disclosed a planarization metal conductive line manufacturing process to improve the adhesion and to reduce the pinhole formation. However, the planarization process needs additional processing steps and materials, and the result of the planarization may further increase the parasitic capacitance. In summary, improving the material is the proper way to solve the above-mentioned problems.
According to the above-mentioned requirements, aluminum, which has low resistance and is simply to be used in the process. Since aluminum may generate hillocks when applying high temperature and large current, the conductive line made of aluminum is then shortened or opened. This may result in the reliability problem of the flat panel display. Alternatively, copper, which has lower resistance, is another preferred material. However, copper is bad adhering to the glass substrate, the surface of copper is easy to be oxidized, and copper is hard to be etched away. Therefore, the change of the manufacturing process or the composition is inevitable, which results in the increase of the manufacturing cost and complexity. This is not matching the requirement for mass production of organic electroluminescent device.
Besides, in the manufacturing process of a TFT-LCD, the three-layer structure, such as Cr/Al/Cr or Mo/Al/Mo, is used as the material of the conductive lines, so as to prevent the above-mentioned problems. For manufacturing such conductive lines, two different etchants are necessary. Firstly, a first etchant is used to etch the upper metal chromium (Cr) or molybdenum (Mo), and a second etchant is then used to etch the middle metal aluminum (Al). Finally, the first etchant is used again to etch the bottom metal chromium (Cr) or molybdenum (Mo). Thus, three times of etching processes are necessary, resulting in complex manufacturing processes and increasing the cost. In practice, the three-layer structure is unsuitable for the industrial application. This invention is therefore to provide a display panel and an electrode panel and an electrode substrate thereof, which can solve the above-mentioned problems.